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The effects of skeletal asymmetry on interpreting biologic variation and taphonomy in the fossil record

Published online by Cambridge University Press:  31 December 2018

Brandon P. Hedrick
Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, U.S.A. E-mail:,
Emma R. Schachner
Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, U.S.A. E-mail:
Gabriel Rivera
Department of Biology, Creighton University, Omaha, Nebraska 68178,
Peter Dodson
Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, U.S.A., and Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, U.S.A. E-mail:
Stephanie E. Pierce
Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, U.S.A. E-mail:,


Biologic asymmetry is present in all bilaterally symmetric organisms as a result of normal developmental instability. However, fossilized organisms, which have undergone distortion due to burial, may have additional asymmetry as a result of taphonomic processes. To investigate this issue, we evaluated the magnitude of shape variation resulting from taphonomy on vertebrate bone using a novel application of fluctuating asymmetry. We quantified the amount of total variance attributed to asymmetry in a taphonomically distorted fossil taxon and compared it with that of three extant taxa. The fossil taxon had an average of 27% higher asymmetry than the extant taxa. In spite of the high amount of taphonomic input, the major axes of shape variation were not greatly altered by removal of the asymmetric component of shape variation. This presents the possibility that either underlying biologic trends drive the principal directions of shape change irrespective of asymmetric taphonomic distortion or that the symmetric taphonomic component is large enough that removing only the asymmetric component is inadequate to restore fossil shape. Our study is the first to present quantitative data on the relative magnitude of taphonomic shape change and presents a new method to further explore how taphonomic processes impact our interpretation of the fossil record.

Paleobiology , Volume 45 , Issue 1 , February 2019 , pp. 154 - 166
Copyright © 2018 The Paleontological Society. All rights reserved 

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Present address: Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, U.K.

Data available from the Dryad Digital Repository:


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